Fuel cell stack

ABSTRACT

A fuel cell stack includes: a cell stacked body in which fuel cells are stacked in multiple layers; an end plate by which the fuel cells are fastened; and a dummy cell interposed between the cell stacked body and the end plate, wherein the end plate includes a gas inlet for introducing a reactant gas from an outside, and a gas outlet for discharging the reactant gas to the outside, and the dummy cell includes a gas supply manifold delivering the reactant gas having passed through the gas inlet to the cell stacked body, a gas exhaust manifold delivering the reactant gas having passed through the cell stacked body to the gas outlet, and a bypass channel connecting the gas supply manifold to the gas exhaust manifold and being partially curved to allow the condensed water to be collected.

CROSS-REFERENCE TO RELATED APPLICATION

This application is the divisional of U.S. patent application Ser. No.15/828,116 filed on Nov. 30, 2017, which is based on and claims thebenefit of priority to Korean Patent Application No. 10-2017-0065596,filed on May 26, 2017, with the Korean Intellectual Property Office, thedisclosures of which are incorporated herein in their entirety byreference.

TECHNICAL FIELD

The present disclosure relates to a fuel cell stack.

BACKGROUND

A fuel cell that is a main power supply source of a fuel cell system isa device that produces electricity while producing water by receivinghydrogen, which is a fuel, and oxygen, which is an oxidizing agent. Highpurity hydrogen is supplied from a hydrogen storage tank to an anode(fuel electrode) of a fuel cell stack, and air in the atmospherecontaining, e.g., oxygen, is directly supplied to a cathode (airelectrode) of the fuel cell stack by an air supply device such as an aircompressor.

Hydrogen supplied to the anode is split into hydrogen ions (protons) andelectrons by a catalyst of the anode, and the protons are conductedthrough a polymer electrolyte membrane to the cathode. Oxygen in the airsupplied to the cathode is combined with the electrons which havetraveled to the cathode through an external circuit to form water andgenerate electrical energy.

As the polymer electrolyte membrane is sufficiently wet with moisture,ion conductivity increases and loss due to resistance decreases. Inaddition, when the supply of a reactant gas having a low relativehumidity continues, the polymer electrolyte membrane becomes dry and mayno longer be used. Therefore, humidification of the reactant gas isessential in the fuel cell system, and thus the fuel cell system maygenerally be provided with a humidifier capable of humidifying thereactant gas.

Meanwhile, the reactant gas humidified by the humidifier may be suppliedto the fuel cell stack through a gas supply line. In the gas supplyline, moisture contained in the reactant gas may be condensed due to lowambient temperature, to foam condensed water. In addition, the condensedwater generated during the humidification of the reactant gas in thehumidifier may flow into the gas supply line together with the reactantgas. The condensed water may flow, together with the reactant gas, intothe interior of the fuel cell stack, and then flow into fuel cells. Mostof the condensed water flowing into the interior of the fuel cell stackmay flow intensively into a fuel cell located at an inlet side of thefuel cell stack. In the inlet side fuel cell of the fuel cell stack,continuous presence of excessive condensed water may frequently causedegradation of the anode and the cathode (hereinafter referred to as the“electrodes”). The degradation of the electrodes is a key factor indecreasing the durability of the fuel cell system.

Therefore, a conventional fuel cell stack includes a dummy cell disposedbetween the inlet side fuel cell and an end plate in order to preventthe degradation of the electrodes. The dummy cell includes a gas supplymanifold guiding the reactant gas supplied from the outside of the fuelcell stack to the fuel cells, a gas exhaust manifold guiding thereactant gas having passed through the fuel cells to the outside, and abypass channel connecting the gas supply manifold to the gas exhaustmanifold to guide the condensed water passing through the gas supplymanifold to the gas exhaust manifold. Due to the presence of the dummycell, the condensed water introduced into the interior of the fuel cellstack fails to enter the fuel cells, and is discharged to the outside ofthe fuel cell stack through the bypass channel of the dummy cell.However, not only the condensed water but also part of the reactant gasintroduced into the interior of the fuel cell stack may be forced toflow into the bypass channel.

Therefore, in the conventional fuel cell stack, part of the reactant gasmay be discharged to the outside of the fuel cell stack through thebypass channel without reaching the fuel cells, and thus the efficiencyof the fuel cell system may be lowered.

SUMMARY

The present disclosure has been made to solve the above mentionedproblems occurring in the prior art while advantages achieved by theprior art are maintained intact.

An aspect of the present disclosure provides a fuel cell stack having anovel structure for preventing loss of a reactant gas through a bypasschannel that is designed to discharge condensed water introduced into aninterior of the fuel cell stack to an outside of the fuel cell stack.

According to an aspect of the present disclosure, a fuel cell stackincludes: a cell stacked body in which a plurality of fuel cells arestacked in multiple layers; an end plate by which the plurality of fuelcells are fastened; and a dummy cell interposed between the cell stackedbody and the end plate, in which the end plate includes a gas inletthrough which a reactant gas supplied from an outside of the fuel cellstack is introduced, and a gas outlet through which the reactant gas isdischarged to the outside, and the dummy cell includes a gas supplymanifold delivering the reactant gas having passed through the gas inletto the cell stacked body, a gas exhaust manifold delivering the reactantgas having passed through the cell stacked body to the gas outlet, and abypass channel connecting the gas supply manifold to the gas exhaustmanifold to guide condensed water introduced to the gas supply manifoldto the gas exhaust manifold and being partially curved to allow thecondensed water to be collected.

The bypass channel may include one or more valley portions curved toallow the condensed water to be collected.

The gas exhaust manifold may be spaced apart from the gas supplymanifold by a predetermined distance in the direction of gravity, andeach of the one or more valley portions may be concavely curved in adirection of gravity.

The bypass channel may further include one or more ridge portionsconvexly curved in an opposite direction of gravity.

Each of the one or more ridge portions may be positioned between the oneor more valley portions or between any one of the one or more valleyportions and the gas exhaust manifold.

The one or more valley portions and the one or more ridge portions maybe positioned such that an inflection point of a valley portion isspaced apart from an inflection point of a ridge portion by apredetermined distance in the direction of gravity.

The bypass channel may further include an inflow channel providedbetween the gas supply manifold and the one or more valley portions toguide the condensed water to the one or more valley portions, and anoutflow channel provided between the one or more valley portions and thegas exhaust manifold to guide the condensed water to the gas exhaustmanifold.

The inflow channel and the outflow channel may be downwardly inclinedand upwardly inclined in the direction of gravity.

The inflow channel may include a plurality of unit inflow channelsparallel to each other between the gas supply manifold and the one ormore valley portions.

A sum of sectional areas of all of the plurality of unit inflow channelsmay be greater than a sectional area of each of the one or more valleyportions.

The outflow channel may include a plurality of unit outflow channelsparallel to each other between the one or more valley portions and thegas exhaust manifold.

A sum of sectional areas of all of the plurality of unit outflowchannels may be greater than a sectional area of each of the one or morevalley portions.

Each of the one or more valley portions may include a plurality of unitvalley portions parallel to each other.

A sum of sectional areas of all of the plurality of unit valley portionsmay be greater than a sectional area of the inflow channel.

The gas inlet may include a hydrogen inlet through which hydrogensupplied from the outside is introduced, the gas outlet may include ahydrogen outlet through which the hydrogen is discharged to the outside,the gas supply manifold may include a hydrogen supply manifolddelivering the hydrogen having passed through the hydrogen inlet to thecell stacked body, the gas exhaust manifold may include a hydrogenexhaust manifold delivering the hydrogen having passed through the cellstacked body to the hydrogen outlet, and the bypass channel may includea first bypass channel provided in one surface of the dummy cell toconnect the hydrogen supply manifold to the hydrogen exhaust manifold.

The gas inlet may include an air inlet through which air supplied fromthe outside is introduced, the gas outlet may include an air outletthrough which the air is discharged to the outside, the gas supplymanifold may include an air supply manifold delivering the air havingpassed through the air inlet to the cell stacked body, the gas exhaustmanifold may include an air exhaust manifold delivering the air havingpassed through the cell stacked body to the air outlet, and the bypasschannel may include a second bypass channel provided in another surfaceof the dummy cell to connect the air supply manifold to the air exhaustmanifold.

The dummy cell may include a gas diffusion layer, a first bipolar plateattached to one surface of the gas diffusion layer, and a second bipolarplate attached to another surface of the gas diffusion layer. Thehydrogen supply manifold, the air supply manifold, the hydrogen exhaustmanifold, and the air exhaust manifold may be provided in each of thefirst bipolar plate and the second bipolar plate. The first bypasschannel may be provided in one surface of one bipolar plate of the firstand second bipolar plates, and the second bypass channel may be providedin one surface of another bipolar plate of the first and second bipolarplates.

According to another aspect of the present disclosure, a fuel cell stackincludes: a cell stacked body in which a plurality of fuel cells arestacked in multiple layers; and an end plate by which the plurality offuel cells are fastened, the end plate including an open end platedisposed at one end of the cell stacked body and a closed end platedisposed at another end of the cell stacked body, wherein the open endplate includes a gas inlet delivering a reactant gas supplied from anoutside of the fuel cell stack to the cell stacked body, a gas outletdischarging the reactant gas having passed through the cell stacked bodyto the outside, and a bypass channel connecting the gas inlet to the gasoutlet to guide condensed water introduced to the gas inlet to the gasoutlet and being partially curved to allow the condensed water to becollected.

The bypass channel may include one or more valley portions curved toallow the condensed water to be collected.

The gas outlet may be spaced apart from the gas inlet by a predetermineddistance in a direction of gravity, and each of the one or more valleyportions may be concavely curved in the direction of gravity.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentdisclosure will be more apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings:

FIG. 1 illustrates a cross-sectional view of a fuel cell stack accordingto a first exemplary embodiment of the present disclosure;

FIG. 2 illustrates a stacked structure of fuel cells and a dummy cellillustrated in FIG. 1;

FIG. 3 illustrates an exploded perspective view of the fuel cell stackillustrated in FIG. 1;

FIG. 4 illustrates a plan view of a first bipolar plate illustrated inFIG. 3;

FIG. 5 illustrates a plan view of a second bipolar plate illustrated inFIG. 3;

FIG. 6 illustrates a plan view of a first bipolar plate of a fuel cellstack according to a second exemplary embodiment of the presentdisclosure;

FIG. 7 illustrates a plan view of a first bipolar plate of a fuel cellstack according to a third exemplary embodiment of the presentdisclosure;

FIG. 8 illustrates a plan view of a first bipolar plate of a fuel cellstack according to a fourth exemplary embodiment of the presentdisclosure;

FIG. 9 illustrates a plan view of a first bipolar plate of a fuel cellstack according to a fifth exemplary embodiment of the presentdisclosure;

FIG. 10 illustrates a cross-sectional view of a fuel cell stackaccording to a sixth exemplary embodiment of the present disclosure;

FIG. 11 illustrates an exploded perspective view of the fuel cell stackillustrated in FIG. 10;

FIG. 12 illustrates a cross-sectional view of an open end plateillustrated in FIG. 11, taken along line I-I′; and

FIG. 13 illustrates a cross-sectional view of an open end plateillustrated in FIG. 11, taken along line II-II′.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments of the present disclosure will bedescribed in detail with reference to the accompanying drawings. In thedrawings, the same reference numerals will be used throughout todesignate the same or equivalent elements. In addition, a detaileddescription of well-known techniques associated with the presentdisclosure will be ruled out in order not to unnecessarily obscure thegist of the present disclosure.

Terms such as first, second, A, B, (a), and (b) may be used to describethe elements in exemplary embodiments of the present disclosure. Theseterms are only used to distinguish one element from another element, andthe intrinsic features, sequence or order, and the like of thecorresponding elements are not limited by the terms. Unless otherwisedefined, all terms used herein, including technical or scientific terms,have the same meanings as those generally understood by those withordinary knowledge in the field of art to which the present disclosurebelongs. Such terms as those defined in a generally used dictionary areto be interpreted as having meanings equal to the contextual meanings inthe relevant field of art, and are not to be interpreted as having idealor excessively formal meanings unless clearly defined as having such inthe present application.

FIG. 1 illustrates a cross-sectional view of a fuel cell stack accordingto a first exemplary embodiment of the present disclosure. FIG. 2illustrates a stacked structure of fuel cells and a dummy cellillustrated in FIG. 1, and FIG. 3 illustrates an exploded perspectiveview of the fuel cell stack illustrated in FIG. 1.

Referring to FIG. 1, a fuel cell stack 1, according to the firstexemplary embodiment of the present disclosure, includes a cell stackedbody 110 in which a plurality of fuel cells 111 are stacked in multiplelayers, an end plate 120 by which the fuel cells 111 are fastened, and adummy cell 130 interposed between the cell stacked body 110 and the endplate 120 and having a bypass channel 137 that is formed to dischargecondensed water E introduced into the fuel cell stack 1 to the outsideof the fuel cell stack 1.

The cell stacked body 110 includes, as illustrated in FIG. 1, theplurality of fuel cells 111 that are stacked in multiple layers in apredetermined direction. As illustrated in FIG. 2, each of the fuelcells 111 includes a membrane electrode assembly 112, gas diffusionlayers 113 attached to both external surfaces of the membrane electrodeassembly 112, and bipolar plates 114 attached to external surfaces ofthe gas diffusion layers 113.

The membrane electrode assembly 112 includes a polymer electrolytemembrane 112 a, an anode (fuel electrode) 112 b attached to one surfaceof the polymer electrolyte membrane 112 a, and a cathode (air electrode)112 c attached to the other surface of the polymer electrolyte membrane112 a.

Each of the gas diffusion layers 113 may be attached to any one of anexternal surface of the anode 112 b and an external surface of thecathode 112 c.

Each of the bipolar plates 114 may be attached to an external surface ofany one of the gas diffusion layers 113. A gasket k for airtightness maybe interposed between the bipolar plate 114 and the gas diffusion layer113 that are adjacent to each other.

The bipolar plates 114 may be provided to circulate a reactant gas G anda coolant C delivered from an open end plate 121 to be described laterto the fuel cells 111, respectively. To this end, as illustrated in FIG.3, each of the bipolar plates 114 includes a gas supply manifold 115supplying the reactant gas G supplied to the cell stacked body 110 tothe electrodes of each fuel cell 111, a coolant supply manifold 116supplying the coolant C supplied to the cell stacked body 110 to acoolant channel (not shown) of each fuel cell 111, a gas exhaustmanifold 117 discharging the reactant gas G having passed through theelectrodes of each fuel cell 111 from the cell stacked body 110, and acoolant exhaust manifold 118 discharging the coolant C having passedthrough the coolant channel from the cell stacked body 110.

In addition, as illustrated in FIG. 3, the gas supply manifold 115includes a hydrogen supply manifold 115 a supplying hydrogen (H₂)supplied to the cell stacked body 110 to the anode 112 b of each fuelcell 111, and an air supply manifold 115 b supplying air A supplied tothe cell stacked body 110 to the cathode 112 c of each fuel cell 111.Symmetrically, as illustrated in FIG. 3, the gas exhaust manifold 117includes a hydrogen exhaust manifold 117 a discharging the hydrogen (H₂)having passed through the anode 112 b of each fuel cell 111 from thecell stacked body 110, and an air exhaust manifold 117 b discharging theair A having passed through the cathode 112 c of each fuel cell 111 fromthe cell stacked body 110.

In order to smoothly discharge the water produced during powergeneration from the fuel cells 111, the gas exhaust manifold 117 may bespaced apart from the gas supply manifold 115 by a predetermineddistance in the direction of gravity.

For example, the hydrogen supply manifold 115 a may be formed in anupper portion of one side of the bipolar plate 114, and the air supplymanifold 115 b may be formed in an upper portion of the other side ofthe bipolar plate 114.

For example, the hydrogen exhaust manifold 117 a may be formed in alower portion of the other side of the bipolar plate 114, and the airexhaust manifold 117 b may be formed in a lower portion of one side ofthe bipolar plate 114.

For example, the coolant supply manifold 116 may be formed between thehydrogen supply manifold 115 a and the air exhaust manifold 117 b, andthe coolant exhaust manifold 118 may be formed between the air supplymanifold 115 b and the hydrogen exhaust manifold 117 a.

As illustrated in FIG. 3, the fuel cells 111 may be stacked in multiplelayers in a predetermined direction such that the same kind of manifolds115, 116, 117, and 118 communicate with each other. The reactant gas Gand the coolant C supplied from the outside through inlets 123 and 124of the open end plate 121 may circulate in the fuel cells 111 throughthe manifolds 115, 116, 117, and 118.

The end plate 120 may be used to fasten the fuel cells 111, and may beprovided to supply the reactant gas G and the coolant C from the outsideto the fuel cells 111 or discharge the reactant gas G and the coolant Chaving passed through the fuel cells 111 to the outside. To this end,the end plate 120 includes, as illustrated in FIG. 3, the open end plate121 disposed at one end of the cell stacked body 110, and a closed endplate 122 disposed at the other end of the cell stacked body 110.

The open end plate 121 may be provided to supply the reactant gas G andthe coolant C supplied from external supply sources to the fuel cells111 or discharge the reactant gas G and the coolant C having passedthrough the fuel cells 111 to the outside. To this end, the open endplate 121 includes, as illustrated in FIG. 3, a gas inlet 123 throughwhich the reactant gas G supplied from an external gas supply source isintroduced, a gas outlet 125 through which the reactant gas G dischargedfrom the cell stacked body 110 is discharged to the outside, a coolantinlet 124 through which the coolant C supplied from an external coolantsupply source is introduced, and a coolant outlet 126 through which thecoolant C discharged from the cell stacked body 110 is discharged to theoutside.

In addition, the gas inlet 123 includes, as illustrated in FIG. 3, ahydrogen inlet 123 a through which the hydrogen (H₂) supplied from anexternal hydrogen supply source is introduced, and an air inlet 123 bthrough which the air A supplied from an external air supply source isintroduced. Symmetrically, the gas outlet 125 includes, as illustratedin FIG. 3, a hydrogen outlet 125 a through which the hydrogen (H₂)discharged from the cell stacked body 110 is discharged to the outside,and an air outlet 125 b through which the air A discharged from the cellstacked body 110 is discharged to the outside.

The inlets 123 and 124 and the outlets 125 and 126 may be positioned tocorrespond to the manifolds 115, 116, 117, and 118 of the cell stackedbody 110 so as to communicate with the manifolds 115, 116, 117, and 118of the cell stacked body 110.

For example, the hydrogen inlet 123 a may be formed in an upper portionof one side of the open end plate 121 to communicate with the hydrogensupply manifold 115 a of the cell stacked body 110, and the air inlet123 b may be formed in an upper portion of the other side of the openend plate 121 to communicate with the air supply manifold 115 b.

For example, the hydrogen outlet 125 a may be formed in a lower portionof the other side of the open end plate 121 to communicate with thehydrogen exhaust manifold 117 a, and the air outlet 125 b may be formedin a lower portion of one side of the open end plate 121 to communicatewith the air exhaust manifold 117 b.

For example, the coolant inlet 124 may be formed between the hydrogeninlet 123 a and the air outlet 125 b to communicate with the coolantsupply manifold 116, and the coolant outlet 126 may be formed betweenthe air inlet 123 b and the hydrogen outlet 125 a to communicate withthe coolant exhaust manifold 118.

The inlets 123 and 124 may be used to supply the reactant gas G and thecoolant C supplied from the outside to the manifolds 115 and 116 of thecell stacked body 110, and the outlets 125 and 126 may be used todischarge the reactant gas G and the coolant C discharged from themanifolds 117 and 118 of the cell stacked body 110 to the outside.

As illustrated in FIG. 3, the closed end plate 122 may be provided toseal the manifolds 115, 116, 117, and 118 of the cell stacked body 110.

As illustrated in FIG. 3, the open end plate 121 may be disposed at oneend of the cell stacked body 110 to allow the inlets 123 and 124 and theoutlets 125 and 126 to communicate with the manifolds 115, 116, 117, and118 of the cell stacked body 110, and the closed end plate 122 may bedisposed at the other end of the cell stacked body 110 to close themanifolds 115, 116, 117, and 118 of the cell stacked body 110. In otherwords, the cell stacked body 110 may be interposed between the open endplate 121 and the closed end plate 122. The open end plate 121 and theclosed end plate 122 may be fastened by a long bolt or another fasteningmember. Thus, the fuel cells 111 of the cell stacked body 110 may befastened by the open end plate 121 and the closed end plate 122.

The dummy cell 130 includes, as illustrated in FIG. 2, a gas diffusionlayer 131, a first bipolar plate 132 a attached to one surface of thegas diffusion layer 131, and a second bipolar plate 132 b attached tothe other surface of the gas diffusion layer 131. The dummy cell 130differs from the fuel cells 111 in that the former does not include themembrane electrode assembly 112 and cannot produce electricity. Thedummy cell 130 may be interposed between an inlet-side fuel cell 111′located at the foremost end of the cell stacked body 110 among the fuelcells 111 of the cell stacked body 110 and the open end plate 121, asillustrated in FIG. 3.

Each of the first bipolar plate 132 a and the second bipolar plate 132 bmay be provided to selectively discharge the condensed water E, which isintroduced to the interior of the fuel cell stack 1 together with thereactant gas G, to the outside. In other words, each of the firstbipolar plate 132 a and the second bipolar plate 132 b may be providedto allow only the reactant gas G to reach the fuel cells 111 and allowthe condensed water E to be discharged to the outside by the dummy cell130 without reaching the fuel cells 111. To this end, the dummy cell 130includes, as illustrated in FIG. 3, a gas supply manifold 133 deliveringthe reactant gas G having passed through the gas inlet 123 of the openend plate 121 to the gas supply manifold 115 of the cell stacked body110, a coolant supply manifold 134 delivering the coolant C havingpassed through the coolant inlet 124 of the open end plate 121 to thecoolant supply manifold 116 of the cell stacked body 110, a gas exhaustmanifold 135 delivering the reactant gas G discharged from the gasexhaust manifold 117 of the cell stacked body 110 to the gas outlet 125of the open end plate 121, a coolant exhaust manifold 136 delivering thecoolant C discharged from the coolant exhaust manifold 118 of the cellstacked body 110 to the coolant outlet 126 of the open end plate 121,and a bypass channel 137 connecting the gas supply manifold 133 to thegas exhaust manifold 135 to guide the condensed water E introduced intothe gas supply manifold 133 to the gas exhaust manifold 135, and beingpartially curved to allow the condensed water E to be collected.

In addition, as illustrated in FIG. 3, the gas supply manifold 133includes a hydrogen supply manifold 133 a delivering the hydrogen (H₂)having passed through the gas inlet 123 of the open end plate 121 to thehydrogen supply manifold 115 a of the cell stacked body 110, and an airsupply manifold 133 b delivering the air A having passed through the airinlet 123 b of the open end plate 121 to the air supply manifold 115 bof the cell stacked body 110, and the gas exhaust manifold 135 includesa hydrogen exhaust manifold 135 a delivering the hydrogen (H₂)discharged from the hydrogen exhaust manifold 117 a of the cell stackedbody 110 to the hydrogen outlet 125 a of the open end plate 121, and anair exhaust manifold 135 b delivering the hydrogen (H₂) discharged fromthe air exhaust manifold 117 b of the cell stacked body 110 to the airoutlet 125 b of the open end plate 121.

The manifolds 133, 134, 135, and 136 of the dummy cell 130 may bepositioned to correspond to the manifolds 115, 116, 117, and 118 of thecell stacked body 110 so as to communicate with the inlets 123 and 124and the outlets 125 and 126 of the open end plate 121 and the manifolds115, 116, 117, and 118 of the cell stacked body 110, respectively.

For example, the hydrogen supply manifold 133 a may be formed in anupper portion of one side of each of the first bipolar plate 132 a andthe second bipolar plate 132 b to communicate with the hydrogen inlet123 a and the hydrogen supply manifold 115 a, and the air supplymanifold 133 b may be formed in an upper portion of the other side ofeach of the first bipolar plate 132 a and the second bipolar plate 132 bto communicate with the air inlet 123 b and the air supply manifold 115b.

For example, the hydrogen exhaust manifold 135 a may be formed in alower portion of the other side of each of the first bipolar plate 132 aand the second bipolar plate 132 b to communicate with the hydrogenoutlet 125 a and the hydrogen exhaust manifold 117 a, and the airexhaust manifold 135 b may be formed in a lower portion of one side ofeach of the first bipolar plate 132 a and the second bipolar plate 132 bto communicate with the air outlet 125 b and the air exhaust manifold117 b.

For example, the coolant supply manifold 134 may be formed between thehydrogen supply manifold 133 a and the air exhaust manifold 135 b tocommunicate with the coolant inlet 124 and the coolant supply manifold116, and the coolant exhaust manifold 136 may be formed between the airsupply manifold 133 b and the hydrogen exhaust manifold 135 a tocommunicate with the coolant outlet 126 and the coolant exhaust manifold118.

As described above, in order to smoothly discharge the water from thefuel cells 111, the gas exhaust manifold 117 of the cell stacked body110 may be spaced apart from the gas supply manifold 115 by apredetermined distance in the direction of gravity. The gas exhaustmanifold 135 of the dummy cell 130 may also be spaced apart from the gassupply manifold 133 by a predetermined distance in the direction ofgravity. Hereinafter, the bypass channel 137 will be described on thepremise that the gas supply manifold 133 and the gas exhaust manifold135 are disposed in the aforementioned relative positions (to be highand low).

The condensed water E produced through the condensation of moisturecontained in the reactant gas G may also flow into the gas inlet 123 ofthe open end plate 121. If the condensed water E is supplied to the fuelcells 111, the condensed water E may cause the degradation of the anode112 b and the cathode 112 c to reduce the durability of the fuel cellsystem. In order to solve this problem, the dummy cell 130 includes thebypass channel 137 bypassing the condensed water E flowing into theinterior of the fuel cell stack 1 to prevent the condensed water E fromreaching the gas supply manifold 115 of the cell stacked body 110,thereby discharging the condensed water E to the outside of the fuelcell stack 1.

The bypass channel 137 may be provided to individually bypass thecondensed water E, which is introduced into the interior of the fuelcell stack 1 together with hydrogen (H₂), and the condensed water E,which is introduced into the interior of the fuel cell stack 1 togetherwith the air A. To this end, the bypass channel 137 includes, asillustrated in FIG. 3, a first bypass channel 137 a formed in onesurface of the dummy cell 130 to guide the condensed water E, which isintroduced into the hydrogen supply manifold 133 a together withhydrogen (H₂), to the hydrogen exhaust manifold 135 a, and a secondbypass channel 137 b formed in the other surface of the dummy cell 130to guide the condensed water E, which is introduced into the air supplymanifold 133 b together with the air A, to the air exhaust manifold 135b. As illustrated in FIG. 3, the first bypass channel 137 a and thesecond bypass channel 137 b may have a symmetrical shape to perform thesame function. Therefore, the first bypass channel 137 a will bedescribed in detail and the second bypass channel 137 b will be brieflydescribed below for convenience of explanation.

FIG. 4 illustrates a plan view of the first bipolar plate illustrated inFIG. 3.

As illustrated in FIG. 4, the first bypass channel 137 a may be recessedin one surface of the first bipolar plate 132 a to connect the hydrogensupply manifold 133 a to the hydrogen exhaust manifold 135 a. Onesurface of the first bipolar plate 132 a may be one of two surfaces ofthe first bipolar plate 132 a in contact with the open end plate 121.Thus, the open end plate 121 may close an opening portion of the firstbypass channel 137 a to maintain airtightness of the first bypasschannel 137 a.

At least a portion of the first bypass channel 137 a may be curved toallow at least a portion of the condensed water E flowing from thehydrogen supply manifold 133 a to the first bypass channel 137 a to becollected in the interior of the first bypass channel 137 a. Forexample, as illustrated in FIG. 4, the first bypass channel 137 aincludes a valley portion 137 c curved to allow the condensed water E tobe collected, a ridge portion 137 d curved between the valley portion137 c and the hydrogen exhaust manifold 135 a to form a predeterminedheight difference H1 with respect to the valley portion 137 c, an inflowchannel 137 e formed between the hydrogen supply manifold 133 a and thevalley portion 137 c to guide the condensed water E introduced into thehydrogen supply manifold 133 a to the valley portion 137 c, and anoutflow channel 137 f formed between the ridge portion 137 d and thehydrogen exhaust manifold 135 a to guide the condensed water E havingpassed through the ridge portion 137 d to the hydrogen exhaust manifold135 a.

The valley portion 137 c may be concavely curved in the direction ofgravity. Symmetrically, the ridge portion 137 d may be convexly curvedin the opposite direction of gravity. A front end of the ridge portion137 d may be connected to a rear end of the valley portion 137 c. Thevalley portion 137 c and the ridge portion 137 d may have thepredetermined height difference H1 such that an inflection point 137 hof the ridge portion 137 d may be spaced apart from an inflection point137 g of the valley portion 137 c in the opposite direction of gravity.

The inflow channel 137 e may be downwardly inclined in the direction ofgravity between the hydrogen supply manifold 133 a and a front end ofthe valley portion 137 c, and connect the hydrogen supply manifold 133 ato the front end of the valley portion 137 c. The outflow channel 137 fmay be downwardly inclined in the direction of gravity between a rearend of the ridge portion 137 d and the hydrogen exhaust manifold 135 a,and connect the rear end of the ridge portion 137 d to the hydrogenexhaust manifold 135 a.

Hereinafter, referring to FIG. 4, a process of discharging the condensedwater E, which is introduced into the interior of the fuel cell stack 1together with hydrogen (H₂), to the outside of the fuel cell stack 1through the first bypass channel 137 a will be described.

First of all, the condensed water E having passed through the hydrogeninlet 123 a may reach the hydrogen supply manifold 133 a together withhydrogen (H₂).

Next, the condensed water E having reached the hydrogen supply manifold133 a may flow into the inflow channel 137 e by gravity. In addition, aportion of hydrogen (H₂) having reached the hydrogen supply manifold 133a may also flow into the inflow channel 137 e.

Thereafter, the condensed water E and the hydrogen (H₂) introduced intothe inflow channel 137 e may flow through the inflow channel 137 e toreach the valley portion 137 c. Since the valley portion 137 c isconcavely curved in the direction of gravity, the condensed water Ehaving reached the valley portion 137 c may be collected in the valleyportion 137 c. As an amount of the condensed water E collected in thevalley portion 137 c increases, the condensed water E may rise in thevalley portion 137 c, a portion of the ridge portion 137 d, and aportion of the inflow channel 137 e (hereinafter referred to as “thevalley portion 137 c and the adjacent portions”), as illustrated in FIG.4. Here, the portion of the ridge portion 137 d refers to a portionbetween the front end of the ridge portion 137 d and the inflectionpoint 137 h of the ridge portion 137 d. As the increased amount ofcondensed water E is collected in the valley portion 137 c and theadjacent portions, at least a portion of the valley portion 137 c andthe adjacent portions may be closed by the condensed water E. Thus,hydrogen (H₂) may pass through the valley portion 137 c and the ridgeportion 137 d to flow into the hydrogen exhaust manifold 135 a beforethe valley portion 137 c and the adjacent portions are closed by thecondensed water E, but the flow of hydrogen (H₂) may be blocked by thecondensed water E after the valley portion 137 c and the adjacentportions are closed by the condensed water E, resulting in a failure inthe flow of hydrogen (H₂) into the hydrogen exhaust manifold 135 a.

Then, the condensed water E collected in the valley portion 137 c mayflow into the hydrogen exhaust manifold 135 a through the outflowchannel 137 f after passing through the inflection point 137 h of theridge portion 137 d when a discharge force thereof is greater than aretention force. The condensed water E introduced into the hydrogenexhaust manifold 135 a through the first bypass channel 137 a may bedischarged to the outside of the fuel cell stack 1, together with thehydrogen discharged from the hydrogen exhaust manifold 117 a of the cellstacked body 110. Thus, the first bypass channel 137 a may prevent thedegradation of the anode 112 b that may be caused by the condensed waterE, thereby improving the durability of the fuel cell system. Inaddition, the first bypass channel 137 a may prevent the hydrogen (H₂)from being discharged to the outside without reaching the fuel cells111, thereby improving the efficiency of the fuel cell system.

Meanwhile, the discharge force refers to a driving force that acts onthe condensed water E to allow the condensed water E to flow from thehydrogen supply manifold 133 a to the hydrogen exhaust manifold 135 a.The discharge force includes a weight of the condensed water E collectedbetween the inflection point 137 g of the valley portion 137 c and afront end of the inflow channel 137 e, and a differential pressurebetween the hydrogen supply manifold 133 a and the hydrogen exhaustmanifold 135 a. In addition, the retention force refers to a resistanceforce that acts on the condensed water E to prevent the condensed waterE from flowing from the hydrogen supply manifold 133 a to the hydrogenexhaust manifold 135 a. The retention force includes a fractional forceacting between the condensed water E collected in the valley portion 137c and the adjacent portions and internal surfaces of the valley portion137 c and the adjacent portions, and a weight of the condensed water Ecollected between the inflection point 137 g of the valley portion 137 cand the inflection point 137 h of the ridge portion 137 d. Thus, byadjusting the height difference H1 between the valley portion 137 c andthe ridge portion 137 d, the differential pressure between the hydrogensupply manifold 133 a and the hydrogen exhaust manifold 135 a, asectional area of the first bypass channel 137 a, and the like, theamount of the condensed water E collected in the first bypass channel137 a may be adjusted to an appropriate level.

FIG. 5 illustrates a plan view of the second bipolar plate illustratedin FIG. 3.

As illustrated in FIG. 5, the second bypass channel 137 b may berecessed in one surface of the second bipolar plate 132 b to connect theair supply manifold 133 b to the air exhaust manifold 135 b. Here, onesurface of the second bipolar plate 132 b may be one of two surfaces ofthe second bipolar plate 132 b in contact with the bipolar plate 114 ofthe inlet-side fuel cell 111′. Thus, an opening portion of the secondbypass channel 137 b may be closed by the bipolar plate 114 of theinlet-side fuel cell 111′ to maintain airtightness of the second bypasschannel 137 b.

At least a portion of the second bypass channel 137 b may be curved toallow at least a portion of the condensed water E flowing from the airsupply manifold 133 b to the second bypass channel 137 b to be collectedin the interior of the second bypass channel 137 b. For example, asillustrated in FIG. 5, the second bypass channel 137 b includes a valleyportion 137 i curved to allow the condensed water E to be collected, aridge portion 137 j curved between the valley portion 137 i and the airexhaust manifold 135 b to form a predetermined height difference H2 withrespect to the valley portion 137 i, an inflow channel 137 k formedbetween the air supply manifold 133 b and the valley portion 137 i toguide the condensed water E introduced into the air supply manifold 133b to the valley portion 137 i, and an outflow channel 137 l formedbetween the ridge portion 137 j and the air exhaust manifold 135 b toguide the condensed water E having passed through the ridge portion 137j to the air exhaust manifold 135 b.

The configuration of the second bypass channel 137 b may be the same asthat of the first bypass channel 137 a described above. Thus, due to theconfiguration of the second bypass channel 137 b, the condensed water Emay be collected in the valley portion 137 i, a portion of the inflowchannel 137 k, and a portion of the ridge portion 137 j and be thengradually guided to the air exhaust manifold 135 b depending onstrengths of the discharge force and the retention force of thecondensed water E, and as the valley portion 137 i and the adjacentportions are closed by the condensed water E, the air A may fail to passthrough the second bypass channel 137 b, and may be delivered to the airsupply manifold 133 b of the cell stacked body 110. Therefore, thesecond bypass channel 137 b may prevent the degradation of the cathode112 c that may be caused by the condensed water E, thereby improving thedurability of the fuel cell system. In addition, the second bypasschannel 137 b may prevent the air A from being discharged to the outsidewithout reaching the fuel cells 111, thereby improving the efficiency ofthe fuel cell system.

FIG. 6 illustrates a plan view of a first bipolar plate of a fuel cellstack, according to a second exemplary embodiment of the presentdisclosure.

A fuel cell stack 2 according to the second exemplary embodiment of thepresent disclosure has the same configuration as that of theabove-described fuel cell stack 1, except that a structure of a bypasschannel is changed. Hereinafter, the bypass channel of the fuel cellstack 2 will be described by explaining a first bypass channel 237 a asan example.

The first bypass channel 237 a may be recessed in one surface of a firstbipolar plate 232 a in contact with the open end plate 121. The firstbypass channel 237 a differs from the first bypass channel 137 a of thefuel cell stack 1 in that the former includes a plurality of valleyportions 237 c and a plurality of ridge portions 237 d.

As illustrated in FIG. 6, the ridge portion 237 d may be positionedbetween a pair of adjacent valley portions 237 c or between a lastvalley portion 237 c and a hydrogen exhaust manifold 235 a. Thus, thecondensed water E introduced into the first bypass channel 237 a may becollected in the valley portions 237 c, a portion of the inflow channel237 e, and portions of the ridge portions 237 d, due to a heightdifference between the valley portions 237 c and the ridge portions 237d.

Since the first bypass channel 237 a includes the plurality of valleyportions 237 c and the plurality of ridge portions 237 d, it may adjustan amount of the condensed water E collected in the first bypass channel237 a to a more appropriate level, compared to the first bypass channel137 a of the fuel cell stack 1.

Meanwhile, non-described reference numerals 233 a, 233 b, 234, 235 b,236, and 237 f denote a hydrogen supply manifold, an air supplymanifold, a coolant supply manifold, an air exhaust manifold, a coolantexhaust manifold, and an outflow channel, respectively.

FIG. 7 illustrates a plan view of a first bipolar plate of a fuel cellstack, according to a third exemplary embodiment of the presentdisclosure.

A fuel cell stack 3 according to the third exemplary embodiment of thepresent disclosure has the same configuration as that of theabove-described fuel cell stack 1, except that a structure of a bypasschannel is changed. Hereinafter, the bypass channel of the fuel cellstack 3 will be described by explaining a first bypass channel 337 a asan example.

The first bypass channel 337 a may be recessed in one surface of a firstbipolar plate 332 a in contact with the open end plate 121. The firstbypass channel 337 a differs from the first bypass channel 137 a of thefuel cell stack 1 in that the former includes a plurality of first unitbypass channels 337 o parallel to each other.

The sectional area and hydraulic diameter of each of the first unitbypass channels 337 o may be less than the sectional area and hydraulicdiameter of the first bypass channel 137 a of the fuel cell stack 1, butthe sum of the sectional areas of all the first unit bypass channels 337o may be greater than the sectional area of the first bypass channel 137a. The first unit bypass channels 337 o may be formed in the firstbipolar plate 332 a when it is difficult to form a single first bypasschannel 337 a having a large sectional area in the first bipolar plate332 a due to processing difficulties, but is not limited thereto. Thefirst unit bypass channels 337 o may increase a contact area between thecondensed water E collected in the interior of the first bypass channel337 a and the internal surface of the first bypass channel 337 a. Thus,the fuel cell stack 3 may increase a frictional force acting between thecondensed water E collected in the interior of the first bypass channel337 a and the internal surface of the first bypass channel 337 a,thereby increasing the retention force of the condensed water.

Meanwhile, non-described reference numerals 333 a, 333 b, 334, 335 a,335 b, 336, 337 c, 337 d, 337 e, and 337 f denote a hydrogen supplymanifold, an air supply manifold, a coolant supply manifold, a hydrogenexhaust manifold, an air exhaust manifold, a coolant exhaust manifold, avalley portion, a ridge portion, an inflow channel, and an outflowchannel, respectively.

FIG. 8 illustrates a plan view of a first bipolar plate of a fuel cellstack according to a fourth exemplary embodiment of the presentdisclosure.

A fuel cell stack 4 according to the fourth exemplary embodiment of thepresent disclosure has the same configuration as that of theabove-described fuel cell stack 1, except that a structure of a bypasschannel is changed. Hereinafter, the bypass channel of the fuel cellstack 4 will be described by explaining a first bypass channel 437 a asan example.

The first bypass channel 437 a may be recessed in one surface of a firstbipolar plate 432 a in contact with the open end plate 121. The firstbypass channel 437 a differs from the first bypass channel 137 a of thefuel cell stack 1 with respect to the structure of a valley portion 437c and a ridge portion 437 d.

The valley portion 437 c includes a plurality of unit valley portions437 o parallel to each other. A front end of each of the unit valleyportions 437 o may be connected to an inflow channel 437 e. The ridgeportion 437 d includes a plurality of unit ridge portions 437 p parallelto each other. A front end of each of the unit ridge portions 437 p maybe connected to a rear end of each of the unit valley portions 437 o,and a rear end of each of the unit ridge portions 437 p may be connectedto an outflow channel 437 f.

The sectional area and hydraulic diameter of each of the unit valleyportions 437 o may be less than the sectional area and hydraulicdiameter of the inflow channel 437 e, but the sum of the sectional areasof all the unit valley portions 437 o may be greater than the sectionalarea of the inflow channel 437 e. In addition, the unit ridge portions437 p may have the same sectional area and hydraulic diameter as thoseof the unit valley portions 437 o. When the entire area of the firstbypass channel 337 a in the above-described fuel cell stack 3 is dividedinto the plurality of first unit bypass channels 337 o, the retentionforce of the condensed water E may be excessively increased, and thus anamount of the condensed water E collected in the first bypass channel337 a may exceed an appropriate level. However, the fuel cell stack 4has a structure in which only the valley portion 437 c and the ridgeportion 437 d, in which the condensed water E is mainly collected, arelimitedly divided into the plurality of unit valley portions 437 o andthe plurality of unit ridge portions 437 p, and thus the retention forceof the condensed water E may be increased to an appropriate level and anamount of the condensed water E collected in the first bypass channelmay be adjusted to an appropriate level.

Meanwhile, non-described reference numerals 433 a, 433 b, 434, 435 a,435 b, 436 denote a hydrogen supply manifold, an air supply manifold, acoolant supply manifold, a hydrogen exhaust manifold, an air exhaustmanifold, and a coolant exhaust manifold, respectively.

FIG. 9 illustrates a plan view of a first bipolar plate of a fuel cellstack according to a fifth exemplary embodiment of the presentdisclosure.

A fuel cell stack 5 according to the fifth exemplary embodiment of thepresent disclosure has the same configuration as that of theabove-described fuel cell stack 1, except that a structure of a bypasschannel is changed. Hereinafter, the bypass channel of the fuel cellstack 5 will be described by explaining a first bypass channel 537 a asan example.

The first bypass channel 537 a may be recessed in one surface of a firstbipolar plate 532 a in contact with the open end plate 121. The firstbypass channel 537 a differs from the first bypass channel 137 a of thefuel cell stack 1 with respect to the structure of an inflow channel 537e and an outflow channel 537 f.

The inflow channel 537 e includes a plurality of unit inflow channels537 o parallel to each other. A front end of each of the unit inflowchannels 537 o may be connected to a hydrogen supply manifold 533 a, anda rear end of each of the unit inflow channels 537 o may be connected toa front end of a valley portion 537 c. The outflow channel 537 fincludes a plurality of unit outflow channels 537 p parallel to eachother. A front end of each of the unit outflow channels 537 p may beconnected to a rear end of a ridge portion 537 d, and a rear end of eachof the unit outflow channels 537 p may be connected to a hydrogenexhaust manifold 535 a.

The sectional area and hydraulic diameter of each of the unit inflowchannels 537 o may be less than the sectional area and hydraulicdiameter of the valley portion 537 c, but the sum of the sectional areasof all the unit inflow channels 537 o may be greater than the sectionalarea of the valley portion 537 c. Thus, a force of hydrogen (H₂) flowinginto the inflow channel 537 e to push the condensed water E collected inthe valley portion 537 c may be increased in proportion to an increasein the sectional area of the inflow channel 537 e. Therefore, the unitinflow channels 537 o may increase the discharge force of the condensedwater E.

The sectional area and hydraulic diameter of each of the unit outflowchannels 537 p may be less than the sectional area and hydraulicdiameter of the valley portion 537 c, but the sum of the sectional areasof all the unit outflow channels 537 p may be greater than the sectionalarea of the valley portion 537 c. Thus, the flow resistance of hydrogen(H₂) passing through the outflow channel 537 f may be reduced inproportion to an increase in the sectional area of the outflow channel537 f. Therefore, the unit outflow channels 537 p may reduce theretention force of the condensed water E.

Meanwhile, non-described reference numerals 533 b, 534, 535 b, and 536denote an air supply manifold, a coolant supply manifold, an air exhaustmanifold, and a coolant exhaust manifold, respectively.

FIG. 10 illustrates a cross-sectional view of a fuel cell stackaccording to a sixth exemplary embodiment of the present disclosure, andFIG. 11 illustrates an exploded perspective view of the fuel cell stackillustrated in FIG. 10.

A fuel cell stack 6 according to a sixth exemplary embodiment of thepresent disclosure has the same configuration as that of theabove-described fuel cell stack 1, except that the dummy cell 30 isremoved, and a bypass channel 627 is formed in an open end plate 621.Hereinafter, the fuel cell stack 6 will be described by focusing on theopen end plate 621.

As illustrated in FIG. 10, the open end plate 621 may be provided tosupply a reactant gas G and a coolant C supplied from external supplysources to fuel cells 611 or discharge the reactant gas G and thecoolant C having passed through the fuel cells 611 to the outside. Inaddition, as illustrated in FIG. 10, the open end plate 621 may beprovided to selectively discharge condensed water E, which is introducedto the interior of the fuel cell stack 6 together with the reactant gasG, to the outside. To this end, the open end plate 621 includes, asillustrated in FIG. 11, a gas inlet 623, a gas outlet 625, a coolantinlet 624, a coolant outlet 626, and a bypass channel 627.

In addition, the gas inlet 623 includes, as illustrated in FIG. 11, ahydrogen inlet 623 a and an air inlet 623 b. Symmetrically, the gasoutlet 625 includes, as illustrated in FIG. 11, a hydrogen outlet 625 aand an air outlet 625 b.

The inlets 623 and 624 and the outlets 625 and 626 may be positioned tocorrespond to manifolds 615, 616, 617, and 618 of a cell stacked body610 so as to communicate with the manifolds 615, 616, 617, and 618 ofthe cell stacked body 610.

For example, the hydrogen inlet 623 a may be formed in an upper portionof one side of the open end plate 621 to communicate with a hydrogensupply manifold 615 a of the cell stacked body 610, and the air inlet623 b may be formed in an upper portion of the other side of the openend plate 621 to communicate with an air supply manifold 615 b of thecell stacked body 610.

For example, the hydrogen outlet 625 a may be formed in a lower portionof the other side of the open end plate 621 to communicate with ahydrogen exhaust manifold 617 a of the cell stacked body 610, and theair outlet 625 b may be formed in a lower portion of one side of theopen end plate 621 to communicate with an air exhaust manifold 617 b ofthe cell stacked body 610.

For example, the coolant inlet 624 may be formed between the hydrogeninlet 623 a and the air outlet 625 b to communicate with a coolantsupply manifold 616 of the cell stacked body 610, and the coolant outlet626 may be formed between the air inlet 623 b and the hydrogen outlet625 a to communicate with a coolant exhaust manifold 618 of the cellstacked body 610.

The bypass channel 627 may connect the gas inlet 623 to the gas outlet625 to guide the condensed water E introduced to the gas inlet 623 tothe gas outlet 625, and may be partially curved to allow the condensedwater E to be collected. The bypass channel 627 may be provided toindividually bypass the condensed water E, which is introduced into theinterior of the fuel cell stack 6 together with hydrogen (H₂), and thecondensed water E, which is introduced into the interior of the fuelcell stack 6 together with the air A. To this end, the bypass channel627 includes, as illustrated in FIG. 11, a first bypass channel 627 aformed in the interior of the open end plate 621 to guide the condensedwater E, which is introduced into the hydrogen inlet 623 a together withthe hydrogen (H₂), to the hydrogen outlet 625 a, and a second bypasschannel 627 b formed in the interior of the open end plate 621 to guidethe condensed water E, which is introduced into the air inlet 623 btogether with the air A, to the air outlet 625 b. As illustrated in FIG.10, the first bypass channel 627 a and the second bypass channel 627 bmay be formed in the interior of the open end plate 621 to be spacedapart from each other by a predetermined distance.

FIG. 12 illustrates a cross-sectional view of an open end plateillustrated in FIG. 11, taken along line I-I′.

At least a portion of the first bypass channel 627 a may be curved toallow at least a portion of the condensed water E flowing from thehydrogen inlet 623 a to the first bypass channel 627 a to be collectedin the interior of the first bypass channel 627 a. For example, asillustrated in FIG. 12, the first bypass channel 627 a includes a valleyportion 627 c curved to allow the condensed water E to be collected, aridge portion 627 d curved between the valley portion 627 c and thehydrogen outlet 625 a to form a predetermined height difference withrespect to the valley portion 627 c, an inflow channel 627 e formedbetween the hydrogen inlet 623 a and the valley portion 627 c to guidethe condensed water E introduced into the hydrogen inlet 623 a to thevalley portion 627 c, and an outflow channel 627 f formed between theridge portion 627 d and the hydrogen outlet 625 a to guide the condensedwater E having passed through the ridge portion 627 d to the hydrogenoutlet 625 a.

Due to the configuration of the first bypass channel 627 a, thecondensed water E introduced from the hydrogen inlet 623 a may becollected in the valley portion 627 c, a portion of the inflow channel627 e, and a portion of the ridge portion 627 d, be then graduallyguided to the hydrogen outlet 625 a depending on strengths of thedischarge force and the retention force of the condensed water E, and bedischarged to the outside. On the other hand, as the valley portion 627c and the adjacent portions are closed by the condensed water E, theentire amount of hydrogen (H₂) may fail to pass through the first bypasschannel 627 a, and may be delivered to the hydrogen supply manifold 615a of the cell stacked body 610. Thus, the first bypass channel 627 a mayprevent the degradation of anodes of the fuel cells 611 that may becaused by the condensed water E, thereby improving the durability of thefuel cell system. In addition, the first bypass channel 627 a mayprevent the hydrogen (H₂) from being discharged to the outside withoutreaching the fuel cells 611, thereby improving the efficiency of thefuel cell system.

FIG. 13 illustrates a cross-sectional view of an open end plateillustrated in FIG. 11, taken along line II-II′.

At least a portion of the second bypass channel 627 b may be curved toallow at least a portion of the condensed water E flowing from the airinlet 623 b to the second bypass channel 627 b to be collected in theinterior of the second bypass channel 627 b. For example, as illustratedin FIG. 13, the second bypass channel 627 b includes a valley portion627 g curved to allow the condensed water E to be collected, a ridgeportion 627 h curved between the valley portion 627 g and the air outlet625 b to form a predetermined height difference with respect to thevalley portion 627 g, an inflow channel 627 i formed between the airinlet 623 b and the valley portion 627 g to guide the condensed water Eintroduced into the air inlet 623 b to the valley portion 627 g, and anoutflow channel 627 j formed between the ridge portion 627 h and the airoutlet 625 b to guide the condensed water E having passed through theridge portion 627 h to the air outlet 625 b.

Due to the configuration of the second bypass channel 627 b, thecondensed water E introduced from the air inlet 623 b may be collectedin the valley portion 627 g, a portion of the inflow channel 627 j, anda portion of the ridge portion 627 h, be then gradually guided to theair outlet 625 b depending on strengths of the discharge force and theretention force of the condensed water E, and be discharged to theoutside. On the other hand, as the valley portion 627 i and the adjacentportions are closed by the condensed water E, the air A may fail to passthrough the second bypass channel 627 b, and may be delivered to the airsupply manifold 615 b of the cell stacked body 610. Thus, the secondbypass channel 627 b may prevent the degradation of cathodes of the fuelcells 611 that may be caused by the condensed water E, thereby improvingthe durability of the fuel cell system. In addition, the second bypasschannel 627 b may prevent the air A from being discharged to the outsidewithout reaching the fuel cells 611, thereby improving the efficiency ofthe fuel cell system.

As set forth above, the fuel cell stack, according to the exemplaryembodiments of the present disclosure, includes the bypass channel thatis designed to discharge the condensed water to the outside of the fuelcell stack, and the bypass channel has a curved structure to allow aportion of the condensed water to be collected. The condensed watercollected in the bypass channel may prevent the reactant gas from beingdischarged to the outside through the bypass channel, and thus theefficiency of the fuel cell system may be improved.

Hereinabove, although the present disclosure has been described withreference to exemplary embodiments and the accompanying drawings, thepresent disclosure is not limited thereto, but may be variously modifiedand altered by those skilled in the art to which the present disclosurepertains without departing from the spirit and scope of the presentdisclosure claimed in the following claims.

What is claimed is:
 1. A fuel cell stack, comprising: a cell stackedbody in which a plurality of fuel cells are stacked in multiple layers;and an end plate by which the plurality of fuel cells are fastened, theend plate including an open end plate disposed at one end of the cellstacked body and a closed end plate disposed at another end of the cellstacked body, wherein the open end plate includes a gas inlet deliveringa reactant gas supplied from an outside of the fuel cell stack to thecell stacked body, a gas outlet discharging the reactant gas havingpassed through the cell stacked body to the outside of the fuel cellstack, and a bypass channel connecting the gas inlet to the gas outletto guide condensed water introduced to the gas inlet to the gas outlet,the bypass channel partially curved to allow the condensed water to becollected.
 2. The fuel cell stack according to claim 1, wherein thebypass channel includes one or more valley portions curved to allow thecondensed water to be collected.
 3. The fuel cell stack according toclaim 2, wherein the gas outlet is spaced apart from the gas inlet by apredetermined distance in a direction of gravity, and each of the one ormore valley portions is concavely curved in the direction of gravity.